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system: Add bindings to configure libc's NSS. 

* gnu/system/nss.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.
* gnu.scm (%public-modules): Add it.
* gnu/system.scm (<operating-system>)[name-service-switch]: New field.
  (etc-directory): Add #:nss parameter and honor it.
  (operating-system-etc-directory): Adjust call accordingly.
* doc/guix.texi (operating-system Reference): Document
  'name-service-switch'.
  (Name Service Switch): New section.
master
Ludovic Courtès 2015-02-04 21:58:15 +01:00
parent ffd74de0c6
commit 996ed73948
5 changed files with 338 additions and 5 deletions
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116
doc/guix.texi
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@ -142,6 +142,7 @@ System Configuration
* Locales:: Language and cultural convention settings.
* Services:: Specifying system services.
* Setuid Programs:: Programs running with root privileges.
* Name Service Switch:: Configuring libc's name service switch.
* Initial RAM Disk:: Linux-Libre bootstrapping.
* GRUB Configuration:: Configuring the boot loader.
* Invoking guix system:: Instantiating a system configuration.
@ -3642,6 +3643,7 @@ instance to support new system services.
* Locales:: Language and cultural convention settings.
* Services:: Specifying system services.
* Setuid Programs:: Programs running with root privileges.
* Name Service Switch:: Configuring libc's name service switch.
* Initial RAM Disk:: Linux-Libre bootstrapping.
* GRUB Configuration:: Configuring the boot loader.
* Invoking guix system:: Instantiating a system configuration.
@ -3827,6 +3829,11 @@ Library Reference Manual}). @xref{Locales}, for more information.
The list of locale definitions to be compiled and that may be used at
run time. @xref{Locales}.
@item @code{name-service-switch} (default: @var{%default-nss})
Configuration of libc's name service switch (NSS)---a
@code{<name-service-switch>} object. @xref{Name Service Switch}, for
details.
@item @code{services} (default: @var{%base-services})
A list of monadic values denoting system services. @xref{Services}.
@ -4648,6 +4655,115 @@ Under the hood, the actual setuid programs are created in the
files in this directory refer to the ``real'' binaries, which are in the
store.
@node Name Service Switch
@subsection Name Service Switch
@cindex name service switch
@cindex NSS
The @code{(gnu system nss)} module provides bindings to the
configuration file of libc's @dfn{name service switch} or @dfn{NSS}
(@pxref{NSS Configuration File,,, libc, The GNU C Library Reference
Manual}). In a nutshell, the NSS is a mechanism that allows libc to be
extended with new ``name'' lookup methods for system databases, which
includes host names, service names, user accounts, and more (@pxref{Name
Service Switch, System Databases and Name Service Switch,, libc, The GNU
C Library Reference Manual}).
The NSS configuration specifies, for each system database, which lookup
method is to be used, and how the various methods are chained
together---for instance, under which circumstances NSS should try the
next method in the list. The NSS configuration is given in the
@code{name-service-switch} field of @code{operating-system} declarations
(@pxref{operating-system Reference, @code{name-service-switch}}).
@c See <http://0pointer.de/lennart/projects/nss-mdns/>.
As an example, the declaration below configures the NSS to use the
@code{nss-mdns} back-end for host name lookups:
@example
(name-service-switch
(hosts (list %files ;first, check /etc/hosts
;; If the above did not succeed, try
;; with 'mdns_minimal'.
(name-service
(name "mdns_minimal")
;; 'mdns_minimal' is authoritative for
;; '.local'. When it returns "not found",
;; no need to try the next methods.
(reaction (lookup-specification
(not-found => return))))
;; Then fall back to DNS.
(name-service
(name "dns"))
;; Finally, try with the "full" 'mdns'.
(name-service
(name "mdns")))))
@end example
The reference for name service switch configuration is given below. It
is a direct mapping of the C library's configuration file format, so
please refer to the C library manual for more information (@pxref{NSS
Configuration File,,, libc, The GNU C Library Reference Manual}).
Compared to libc's NSS configuration file format, it has the advantage
not only of adding this warm parenthetic feel that we like, but also
static checks: you'll know about syntax errors and typos as soon as you
run @command{guix system}.
@defvr {Scheme Variable} %default-nss
This is the default name service switch configuration, a
@code{name-service-switch} object.
@end defvr
@deftp {Data Type} name-service-switch
This is the data type representation the configuration of libc's name
service switch (NSS). Each field below represents one of the supported
system databases.
@table @code
@item aliases
@itemx ethers
@itemx group
@itemx gshadow
@itemx hosts
@itemx initgroups
@itemx netgroup
@itemx networks
@itemx password
@itemx public-key
@itemx rpc
@itemx services
@itemx shadow
The system databases handled by the NSS. Each of these fields must be a
list of @code{<name-service>} objects (see below.)
@end table
@end deftp
@deftp {Data Type} name-service
This is the data type representing an actual name service and the
associated lookup action.
@table @code
@item name
A string denoting the name service (@pxref{Services in the NSS
configuration,,, libc, The GNU C Library Reference Manual}).
@item reaction
An action specified using the @code{lookup-specification} macro
(@pxref{Actions in the NSS configuration,,, libc, The GNU C Library
Reference Manual}). For example:
@example
(lookup-specification (unavailable => continue)
(success => return))
@end example
@end table
@end deftp
@node Initial RAM Disk
@subsection Initial RAM Disk

1
gnu-system.am
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@ -316,6 +316,7 @@ GNU_SYSTEM_MODULES = \
gnu/system/linux.scm \
gnu/system/linux-initrd.scm \
gnu/system/locale.scm \
gnu/system/nss.scm \
gnu/system/shadow.scm \
gnu/system/vm.scm \
\

3
gnu.scm
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@ -1,5 +1,5 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2014 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2014, 2015 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2015 Joshua S. Grant <jgrant@parenthetical.io>
;;;
;;; This file is part of GNU Guix.
@ -37,6 +37,7 @@
(gnu system linux) ; 'base-pam-services'
(gnu system shadow) ; 'user-account'
(gnu system linux-initrd)
(gnu system nss)
(gnu services)
(gnu services base)
(gnu packages)

10
gnu/system.scm
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@ -47,6 +47,7 @@
#:use-module (gnu services base)
#:use-module (gnu system grub)
#:use-module (gnu system shadow)
#:use-module (gnu system nss)
#:use-module (gnu system locale)
#:use-module (gnu system linux)
#:use-module (gnu system linux-initrd)
@ -137,6 +138,8 @@
(default "en_US.utf8"))
(locale-definitions operating-system-locale-definitions ; list of <locale-definition>
(default %default-locale-definitions))
(name-service-switch operating-system-name-service-switch ; <name-service-switch>
(default %default-nss))
(services operating-system-user-services ; list of monadic services
(default %base-services))
@ -408,7 +411,7 @@ settings for 'guix.el' to work out-of-the-box."
(skeletons '())
(pam-services '())
(profile "/run/current-system/profile")
hosts-file
hosts-file nss
(sudoers ""))
"Return a derivation that builds the static part of the /etc directory."
(mlet* %store-monad
@ -422,10 +425,8 @@ settings for 'guix.el' to work out-of-the-box."
/run/current-system/profile/bin/bash\n"))
(emacs (emacs-site-directory))
(issue (text-file "issue" issue))
;; For now, generate a basic config so that /etc/hosts is honored.
(nsswitch (text-file "nsswitch.conf"
"hosts: files dns\n"))
(name-service-switch->string nss)))
;; Startup file for POSIX-compliant login shells, which set system-wide
;; environment variables.
@ -518,6 +519,7 @@ export ASPELL_CONF=\"dict-dir $HOME/.guix-profile/lib/aspell\"
#:skeletons skeletons
#:issue (operating-system-issue os)
#:locale (operating-system-locale os)
#:nss (operating-system-name-service-switch os)
#:timezone (operating-system-timezone os)
#:hosts-file /etc/hosts
#:sudoers (operating-system-sudoers os)

213
gnu/system/nss.scm 100644
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@ -0,0 +1,213 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2015 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
(define-module (gnu system nss)
#:use-module (rnrs enums)
#:use-module (guix records)
#:use-module (srfi srfi-9)
#:use-module (ice-9 match)
#:export (name-service-switch?
name-service-switch
name-service?
name-service
lookup-specification
%default-nss
%files
%compat
%dns
name-service-switch->string))
;;; Commentary:
;;;
;;; Bindings for libc's name service switch (NSS) configuration.
;;;
;;; Code:
(define-record-type* <name-service> name-service
make-name-service
name-service?
(name name-service-name)
(reaction name-service-reaction
(default (lookup-specification))))
;; Lookup specification (info "(libc) Actions in the NSS Configuration").
(define-enumeration lookup-action
(return continue)
make-lookup-action)
(define-enumeration lookup-status
(success
not-found
unavailable
try-again)
make-lookup-status)
(define-record-type <lookup-status-negation>
(lookup-status-negation status)
lookup-status-negation?
(status lookup-status-negation-status))
(define-record-type <lookup-reaction>
(make-lookup-reaction status action)
lookup-reaction?
(status lookup-reaction-status)
(action lookup-reaction-action))
(define-syntax lookup-reaction
(syntax-rules (not =>)
((_ ((not status) => action))
(make-lookup-reaction (lookup-status-negation (lookup-status status))
(lookup-action action)))
((_ (status => action))
(make-lookup-reaction (lookup-status status)
(lookup-action action)))))
(define-syntax-rule (lookup-specification reaction ...)
"Return an NSS lookup specification."
(list (lookup-reaction reaction) ...))
;;;
;;; Common name services and default NSS configuration.
;;;
(define %compat
(name-service
(name "compat")
(reaction (lookup-specification (not-found => return)))))
(define %files
(name-service (name "files")))
(define %dns
;; DNS is supposed to be authoritative, so unless it's unavailable, return
;; what it finds.
(name-service
(name "dns")
(reaction (lookup-specification ((not unavailable) => return)))))
;; The NSS. We list all the databases here because that allows us to
;; statically ensure that the user's configuration refers to existing
;; databases. See libc/nss/databases.def for the list of databases. Default
;; values obtained by looking for "DEFAULT_CONFIG" in libc/nss/*.c.
;;
;; Although libc places 'dns' before 'files' in the default configurations of
;; the 'hosts' and 'networks' databases, we choose to put 'files' before 'dns'
;; by default, so that users can override host/address mappings in /etc/hosts
;; and bypass DNS to improve their privacy and escape NSA's MORECOWBELL.
(define-record-type* <name-service-switch> name-service-switch
make-name-service-switch
name-service-switch?
(aliases name-service-switch-aliases
(default '()))
(ethers name-service-switch-ethers
(default '()))
(group name-service-switch-group
(default (list %compat %files)))
(gshadow name-service-switch-gshadow
(default '()))
(hosts name-service-switch-hosts
(default (list %files %dns)))
(initgroups name-service-switch-initgroups
(default '()))
(netgroup name-service-switch-netgroup
(default '()))
(networks name-service-switch-networks
(default (list %files %dns)))
(password name-service-switch-password
(default (list %compat %files)))
(public-key name-service-switch-public-key
(default '()))
(rpc name-service-switch-rpc
(default '()))
(services name-service-switch-services
(default '()))
(shadow name-service-switch-shadow
(default (list %compat %files))))
(define %default-nss
;; Default NSS configuration.
(name-service-switch))
;;;
;;; Serialization.
;;;
(define (lookup-status->string status)
(match status
('success "SUCCESS")
('not-found "NOTFOUND")
('unavailable "UNAVAIL")
('try-again "TRYAGAIN")
(($ <lookup-status-negation> status)
(string-append "!" (lookup-status->string status)))))
(define lookup-reaction->string
(match-lambda
(($ <lookup-reaction> status action)
(string-append (lookup-status->string status) "="
(symbol->string action)))))
(define name-service->string
(match-lambda
(($ <name-service> name ())
name)
(($ <name-service> name reactions)
(string-append name " ["
(string-join (map lookup-reaction->string reactions))
"]"))))
(define (name-service-switch->string nss)
"Return the 'nsswitch.conf' contents for NSS as a string. See \"NSS
Configuration File\" in the libc manual."
(let-syntax ((->string
(syntax-rules ()
((_ name field)
(match (field nss)
(() ;keep the default config
"")
((services (... ...))
(string-append name ":\t"
(string-join
(map name-service->string services))
"\n")))))))
(string-append (->string "aliases" name-service-switch-aliases)
(->string "ethers" name-service-switch-ethers)
(->string "group" name-service-switch-group)
(->string "gshadow" name-service-switch-gshadow)
(->string "hosts" name-service-switch-hosts)
(->string "initgroups" name-service-switch-initgroups)
(->string "netgroup" name-service-switch-netgroup)
(->string "networks" name-service-switch-networks)
(->string "passwd" name-service-switch-password)
(->string "publickey" name-service-switch-public-key)
(->string "rpc" name-service-switch-rpc)
(->string "services" name-service-switch-services)
(->string "shadow" name-service-switch-shadow))))
;;; Local Variables:
;;; eval: (put 'name-service 'scheme-indent-function 0)
;;; eval: (put 'name-service-switch 'scheme-indent-function 0)
;;; End:
;;; nss.scm ends here